I just had a look at your website and it is similar to my theme here: http://www.thevirtualpersonalassistant.com
It took me a while before I figured out where to go to change my images and text.
You need to be using an FTP service rather than just the WordPress platform.
If you’re not using FTP already, you’ll need to Google how to do that.
Once you’ve done that, you’ll need to add the images you want, into the images folder of your theme.
Once that’s done, open the “header.php” file into Dreamweaver, and edit the image file names that are already in there to the image you want to use. For example, if the image you want is called “canal-team.jpg”, that is the image you would have copied into the images folder of your theme, and that is the name you put in your code instead of “/images/slider_img_4.jpg” for example, it will be /images/canal-team.jpg”.
I hope that makes sense.